<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=1200, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div data-user-name="xiaojichao" data-password="hha">test dataset</div>
    <script>
        const oDiv = document.querySelector("div")
        console.log(oDiv.dataset)
        console.log(oDiv.dataset.userName)
        console.log(oDiv.dataset.password)
        oDiv.dataset.userName = 'hahaha'
        console.log(oDiv.dataset.userName)
    </script>
</body>
</html>